SUCKER ROD

Abstract

A sucker rod, including: a rod; a threaded casing disposed outside the rod; a wedge-shaped groove disposed at one end of the rod; an outer connecting screw thread close to the wedge-shaped groove and disposed outside the rod; a wedge-shaped bulge disposed at the other end of the rod; a positioning nut close to the wedge-shaped bulge and matching with the threaded casing and disposed outside the rod; an inner nut flexibly disposed outside the rod between the positioning nut and the wedge-shaped bulge; and an outer nut flexibly disposed outside the rod for cooperation with the threaded casing; a convex plate disposed inside one end of the threaded casing for cooperation with the positioning nut; and an inner connecting screw thread disposed at the other end of the threaded casing for cooperation with the outer connecting screw thread. The sucker rod has a high torsional strength and is stable.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/CN2010/000846 with an international filing date of Jun. 12, 2010, designating the United States, now pending. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a sucker rod used in oil wells of oil fields, and more particularly to a special plug-in sucker rod for driving screw pumps.

2. Description of the Related Art

Conventional sucker rods for driving screw pumps in oil fields include common sucker rods and those having a fan-shaped head. Two common sucker rods are connected using a joint hoop. One end of the joint hoop is connected using threads with one end of a sucker rod, and the other end of the joint hoop is connected using threads with one end of another sucker rod. Because the connection employs a straight thread, the sucker rod has a low torsional strength and is mainly used in pumping production wells in a reciprocating linear motion. When sucker rods having a fan-shaped head rotate in a screw pump well, the connection between the joint hoops and the sucker rods easily loosens and thus accident happens, thereby reducing the work efficiency of screw pumps.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is one objective of the invention to provide a special plug-in sucker rod for screw pumps that has a high torsional strength and is difficult to break off.

To achieve the above objective, in accordance with one embodiment of the invention, there is provided a special plug-in sucker rod for screw pumps comprising a rod and a threaded casing disposed outside the rod, wherein a wedge-shaped groove is disposed at one end of the rod, and an outer connecting screw thread close to the wedge-shaped groove is disposed outside the rod; a wedge-shaped bulge is disposed at the other end of the rod, and a positioning nut close to the wedge-shaped bulge and matching with the threaded casing is disposed outside the rod using a flexible connection.

To further prevent the breaking off of the sucker rod, an inner nut is disposed outside the rod using a flexible connection between the positioning nut and the wedge-shaped bulge. Thus, the threaded casing is stably fixed in the axial direction via the positioning nut and the inner nut.

An outer nut is disposed outside the rod using a flexible connection for cooperation with the threaded casing. The threaded casing is further fixed in the axial direction with the help of the outer nut.

A convex plate is disposed inside one end of the threaded casing for cooperation with the positioning nut, and the other end of the threaded casing is provided with an inner connecting screw thread. The inner connecting screw thread matches with an outer connecting screw thread of one end of another sucker rod. Thus, two sucker rods are connected via the threaded casing which is fixed in the axial direction via the positioning nut.

The flexible connection is a threaded connection, which is convenient for disassembly.

Advantages of the invention are summarized below. The special plug-in sucker rod of screw pumps comprises the rod and the threaded casing disposed outside the rod. The wedge-shaped groove is disposed at one end of the rod, and the outer connecting screw thread close to the wedge-shaped groove is disposed outside the rod. The wedge-shaped bulge is disposed at the other end of the rod, and the positioning nut close to the wedge-shaped bulge and matching with the threaded casing is disposed outside the rod using a flexible connection. The match of the wedge-shaped groove of the sucker rod with the wedge-shaped bulge of another sucker rod achieves the plug-in match of two sucker rods. The connection part of the two sucker rods is surrounded by the threaded casing which fixes the two sucker rods in the axial direction. The connection structure can bear a large torque, thereby improving the torsional strength of the sucker rod in screw pump wells. Furthermore, the positioning nut, the inner nut, and the outer nut further make the threaded casing fixed in the axial direction. Thus, the sucker rod will not loosen and break off, accidents are avoided, work efficiency improved, and the production cost reduced. Therefore, compared with the existing technology, the invention has a prominent substantive feature and notable progress, and the beneficial effect is obvious.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structure diagram of a sucker rod according to one embodiment of the invention; and

FIG. 2 is an assembly diagram of two sucker rods according to one embodiment of the invention.

In the drawings, the following reference numbers are used: 1. Wedge-shaped groove; 2. Outer connecting screw thread; 3. Rod; 4. Outer nut; 5. Convex plate; 6. Positioning nut; 7. Inner nut; 8. Wedge-shaped bulge; 9. Threaded casing; 10. Inner connecting screw thread.

DETAILED DESCRIPTION OF THE EMBODIMENTS

For further illustrating the invention, experiments detailing a sucker rod are described below. It should be noted that the following examples are intended to describe and not to limit the invention.

As shown in FIG. 1, a special plug-in sucker rod of screw pumps comprises a rod 3 and a threaded casing 9 outside the rod 3. A wedge-shaped groove 1 is disposed at one end of the rod 3. An outer connecting screw thread 2 close to the wedge-shaped groove 1 is disposed at one end of the rod 3. A wedge-shaped bulge 8 is disposed at the other end of the rod 3, and a positioning nut 6 close to the wedge-shaped bulge 8 and matching with the threaded casing 9 is disposed using a flexible connection (for example, threaded connection) outside the rod 3. An inner nut 7 is disposed using a flexible connection (for example, threaded connection) outside the rod 3 between the positioning nut 6 and the wedge-shaped bulge 8. An outer nut 4 is disposed using a flexible connection (for example, threaded connection) outside the rod 3 for cooperation with the threaded casing 9. A convex plate 5 is disposed inside one end of the threaded casing 9 for cooperation with the positioning nut 5, and the other end of the threaded casing is provided with an inner connecting screw thread 10 for matching with an outer connecting screw thread 2 of one end of another sucker rod 3.

Assembly process: as shown in FIG. 1 and FIG. 2, first, the outer nut 4 is disposed outside the rod 3 of the sucker rod, and then the threaded casing 9 is disposed. The positioning nut 6 and the inner nut 7 are screwed in turn. The match of the positioning nut 6 and the convex plate 5 of the threaded casing 9 fixes the threaded casing 9 in the axial direction. Thereafter, the wedge-shaped bulge 8 of the rod 3 is plugged into the wedge-shaped groove 1 of the rod 3 of another sucker rod, to achieve the connection of two sucker rods by the connection of the threaded casing 9 and the outer connecting screw thread 2 of the rod 3 of the sucker rod with the wedge-shaped groove 1. Finally, the outer nut 4 is tightened. With the cooperation of the positioning nut 6, the inner nut 7, and the outer nut 4, the threaded casing 9 is firmly fixed in the axial direction and thus the two sucker rods are connected. The connection mode can effectively improve the torsional strength of the sucker rod. The number of the sucker rod is determined by actual needs, and thus a sucker rod pole is formed by a plurality of sequentially-connected sucker rods.

While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

Claims

1. A sucker rod, comprising: wherein

a) a rod;

b) a threaded casing disposed outside the rod;

c) a wedge-shaped groove;

d) an outer connecting screw thread;

e) a wedge-shaped bulge; and

f) a positioning nut;

the wedge-shaped groove is disposed at one end of the rod, and the outer connecting screw thread close to the wedge-shaped groove is disposed outside the rod; and

the wedge-shaped bulge is disposed at the other end of the rod, and a positioning nut close to the wedge-shaped bulge and matching with the threaded casing is disposed outside the rod using a flexible connection.

2. The sucker rod of claim 1, wherein an inner nut is disposed outside the rod using a flexible connection between the positioning nut and the wedge-shaped bulge.

3. The sucker rod of claim 1, wherein an outer nut is disposed outside the rod using a flexible connection for cooperation with the threaded casing.

4. The sucker rod of claim 2, wherein an outer nut is disposed outside the rod using a flexible connection for cooperation with the threaded casing.

5. The sucker rod of claim 3, wherein a convex plate is disposed inside one end of the threaded casing for cooperation with the positioning nut, and the other end of the threaded casing is provided with an inner connecting screw thread.

6. The sucker rod of claim 4, wherein a convex plate is disposed inside one end of the threaded casing for cooperation with the positioning nut, and the other end of the threaded casing is provided with an inner connecting screw thread.

7. The sucker rod of claim 5, wherein the flexible connection is a threaded connection.

8. The sucker rod of claim 6, wherein the flexible connection is a threaded connection.